Vehicular transmissions of the type having at least one countershaft disposed in spaced parallel relationship to a mainshaft to provide a variety of selectable change gear ratios is well known to those skilled in the art. Most commonly the countershaft gears are either integral with or are secured to the countershaft by keys and the like for rotation therewith and the mainshaft gears encircle and are selectively clutchingly engageable for rotation with the mainshaft and have teeth that meshingly engage teeth of a countershaft gear axially aligned therewith. Sortie vehicular transmissions, known in the trade as "twin countershaft transmissions", feature a pair of countershafts in parallel spaced relationship on opposite sides of the mainshaft and have axially aligned countershaft gears whose teeth meshingly engage teeth on the mainshaft gear on opposite sides of the shaft and support the mainshaft gear such that it floats about the mainshaft until selectively clutch thereto. Varying pitch diameters of the axially aligned countershaft and mainshaft gears provide the change gear ratios associated with the particular transmission.
Due to the necessity of having to provide a variety of change gear ratios, it is not uncommon for the countershaft to have a plurality of countershaft gears of varying pitch diameter spaced axially therealong. In some cases, the countershaft gear is an integral part of the countershaft rather than being a separate gear rotated by the countershaft by means of a key or the like.
It is to the type of transmission countershafts having countershaft gears respectively secured in adjacent sections of the countershaft to which the present invention is addressed for the invention enables simplification and cost reduction associated with such countershaft assemblies by eliminating one groove and replacing the separate keys with a singular key whose radial thickness is adapted to account for the absence of the eliminated groove.